1. Field of the Invention
Aspects of the present invention relate to a video coding technology, and in particular, to an apparatus and method of up-converting a frame rate using frames that are decoded from a video decoder and motion information.
2. Description of the Related Art
With the development of information and communication technologies along with the Internet, video communications, short message communications, and voice communications are increasing. However, the conventional short message centered communication methods are insufficient for the diverse needs of customers. Accordingly, multimedia services that can accommodate diverse features of short messages, images, music, etc. are increasingly provided. However, the volume of multimedia data is so immense that mass storage devices and broader bandwidths for data transmission are required. Therefore, in order to transmit multimedia data that include short messages, images, and audio data, a code compression technique is used.
The basic principle of data compression is to eliminate data redundancy. Data can be compressed by eliminating spatial redundancy (such as the repetition of the same color or object), time redundancy (such as when adjacent frames change little in a moving image frame or a same tone is repeated in an audio file); and visual redundancy (which takes into consideration the fact that human beings' vision and perception are not sensitive to high frequency). In a generally known video coding method, time redundancy in video data is eliminated by temporal filtering based on motion compensation, and spatial redundancy is eliminated by spatial transformation.
The resulting video data in which redundancy has been eliminated is lossily compressed according to a quantization process. Finally, the quantized data undergoes entropy coding to be losslessly compressed.
Such video data compressing technique is employed in a variety of devices ranging from large-volume data processing devices (such as digital TVs, DVD players, etc.) to mobile devices for relatively small-volume data processing (such as mobile phones, PDAs (Personal Digital Assistants), digital camcorders, etc.).
In general, as these mobile devices are provided with insufficient data storage space, network communication bandwidth, and data processing capacity, the resolution and frame rate of video data used in these mobile devices tend to be relatively low. Consequently, video images having a low frame rate may look more unnatural to a user when generated on a Liquid Crystal Display (LCD) panel provided in a mobile device.
In order to overcome this problem, a frame rate up conversion technique has been proposed for coded videos. Such a conversion improves a frame rate of a video coded in a specific frame rate. For example, as shown in FIG. 1, if the frame rate of the original frame (the frame of a coded video) is 15 Hz, a video frame having a frame rate of 30 Hz in total can be obtained by adding interpolated frames into each frame. In this case, a method of obtaining interpolated frames from the original frame is a critical issue. However, if interpolated frames are obtained through additional motion estimation (as in an encoder), a substantial amount of calculation is required and is, thus, not suitable for playing the video in a mobile device.
Therefore, it is necessary to realize a frame rate up-conversion without an additional motion estimation process by using motion vectors already included in the coded video.